Retrievable reverse circulation pellet impact drill



May 5, 1959 J. E. oRTLoFF ET AL 2,885,184 RETRIEvABLE REvERsE CIRCULATION PELLET IMPACT DRILL Filed DeC. 29, 1953 E lNvENrons uro/mfr United States Patent RETRIEVABLE REVERSE CIRCULATION PELLET IMPACT DRILL .lohn E. Ortlolf and Fredric H. Deily, Tulsa, Okla., as-

signors, by mesne assignments, to Jersey Production Research Company Application December 29, 1953, Serial No. 400,869

3 Claims. (Cl. Z55-61) This invention concerns a novel drilling apparatus for the drilling of bore holes in the earth. The drill of this invention embodies the principles of what has been called pellet impact drilling and concerns the manner in which solid pellets are circulated in a bore hole so as to forcefully impinge on the bottom of the hole securing a drilling action. The drill of this invention is particularly intended to control fluid flow so as to direct pellets in an annular area Iabout the axis of the bore hole and so as to return the pellets in an upward path along the axis of the bore hole. The drill of this invention is also advantageous in permitting wire line replacement of operative elements of the drill during drilling operations.

In pellet impact drilling, means are required to secure the effective impingement of hard, dense pellets on the bottom of a bore hole propelled by a high velocity fluid jet. The apparatus required to employ this drilling procedure is fundamentally simple in nature. Tubing connected to fluid pumps at the surface of the earth is eX- tended downwardly into a bore hole for connection to a jet nozzle assembly. As will become apparent, the requisite properties of the tubing employed are considerably less stringent in nature than those controlling selection of tubing in rotary drilling. Thus it is not necessary that the tubing be rotated under high torque, nor that the, tubing contribute any substantial weight to the jet nozzle assembly. Consequently, for many applications it is practical to use a flexible hose, and, in any case, lighter weight tubing may be employed than that employed in rotary drilling.

Again, as will become apparent, the fluid to be employed as a propulsive and recirculating agent for the pellets may be selected from a Wide range of gases or liquids. In this connection it is not necessary that the fluid possess properties to lubricate a drill bit or to affect the cutting action of a drill bit. Consequently a reasonable flexibility exists in selecting the type of fluid to be employed. Particularly in the case of shallow hole drilling, it is possible to successfully use a gas as a fluid, for example, air. In other cases it becomes desirable to employ liquids which may range in character from ordinary water to drilling fluids of the character conventionally employed in rotary drilling operations. However, as will be emphasized, it is an important requirement of this drilling procedure that the fluid employed have a low density as compared to the pellets employed.

The drilling fluid is pumped from the surface of the earth through the tubing referred to, to a jet nozzle assembly. The jet nozzle is so designed as to convert the available pumping pressure to the form of velocity energy. Thus a substantial pressure drop is imposed on the fluid in passing through the jet nozzle so as to cause the fluid to be ejected as a high velocity luid jet. ln this connection, when employing a liquid as the drilling fluid, it is generally preferred that the nozzle employed impose a pressure drop of more than about 100 pounds per square inch on the fluid.

The fluid jet referred to is positioned adjacent the` PlatentedMay 5, 1959 bottom of the bore hole at a spaced distance above the bottom. Pellets of a suitable character are then directed into the iluid jet so as to be entrained in the jet. These pellets are then borne by the jet so as to forcibly impinge against the bottom of the bore hole.

The pellets to be employed must have certain critical characteristics. It has been found that the drilling action obtainable from the impact of pellets is largely controlled by the size of the pellets employed. Thus in the case of very small pellets, relatively little drilling action can be obtained. It is therefore necessary to employ the largest pellets practical dependent upon the size of jet nozzle which may be employed, and the ability of the pellets to withstand fracturing. These limitations require that the' pellets to be employed have a size in the general range of about 1/16 of an inch to 1/2 of an inch when employing as gas as the drilling fluid, and about 1A; of an inch to l inch when employing liquid drilling uid.

The pellets to be employed must also have a high density. The drilling action depends upon the kinetic energy of the pellets, which in turn is proportional to the density of the pellets. Again, as well be brought out, in order to recirculate the pellets in the manner contemplated by this invention, it is necessary that the pelletsA rapidly settle from the drilling fluid employed. Since settling rate depends in part upon the density of the pellets, this requirement again dictates use of high density pellets.

The configuration and surface characteristics of the pellets are again critical. It is important that the pellets be substantially spherical in nature and that they have a smooth non-abrasive surface. It is necessary that the pel-1 lets be non-abrasive in nature so as to limit wear of the` jet nozzle assembly through which the pellets are ejected. The same considerations control the configuration of the pellets since sharp corners or edges of any character would cause undue wear of the jet nozzles. In this connection it is funda-mental that a spherical body possesses" the best resistance to fracture due to impact.

The critical requirements of the pellets to be employed may be emphasized from a somewhat different viewpoint. In order to secure an effective impact-pulverization effect, pellets entrained in a high velocity fluid jet must separate readily from the fluid so as to depart from? fluid circulation paths and so as to overcome any fluid cushioning effect. Again, in the circulation system ern-` ployed in this invention, rapid settling of pellets from upflowing fluid is required. These factors may be referred to as the separation characteristics of the pellets in the fluid employed. The separation characteristics of the pellets in large part depend upon the properties of the. pellets which have been emphasized: size, density, smooth surface, and spherical configuration. Inasmuch as the separation characteristics of the pellets depend in part upon the drilling fluid employed, the drilling fluid is preferably a low viscosity, low density fluid consistent with other requirements of the fluid. Practically the pellets must have a density substantially greater than the fluid employed.

Materials which may be used to prepared suitable pellets include iron, steel and other ferrous alloys. Due to the impact resistance required, hard-ness and tough-v ness are essential and brittle materials cannot be employed. Thus, for example, finished ball bearings have been found to be impractical for use in this invention although ball bearing .blanks obtained prior to surface hardening are satisfactory. Due to their high density, tungsten carbide alloys of the less brittle character are attractive for use in the pellets to be employed. Alloys of this character or other dense metals, may be employed as a core material, surfaced by ferrous alloys having the requisite toughness.

of this invention is the :transiter` action on an annular area about the: botg tomof `ambrato hole. lluidcirculation is so arranged with galleta are swept inwardly `and upwardlynn a essaies v tween`the external surface of thecylinder 10 andthe renn'ncinculation pathcausing secondary drilling edects t t tot central portion of the borehole. Ihis principleumay be considered to be circulation in the sense that `normal circulation reverser y wouldibe considered to directprimary drilling `forces at the center o: the bore hole. It may be appreciated that reveraeicirculation pellet direction, obtained `as indicated, `serves toetfectively concentrate the primary drill-` iugi the outer portion of a bore hole where the greatest volume of` materialgmustbezremovedper foot ofladvaneaotthe bit. H y i l drillolthisinvention is alsoparticularly advan-` tageous in makingpractical a wire line retrievable drill arrangement ao `as to facilitate drilling with casing. It` impossible :to replace itself as desired `without necessity for removing` the drill string, casing, `or other support `structure from the bore hole.

...A preferred embodiment is illustrated in theattached in which:`

in elevational detail: Iund stitlltea` two principal elements. The `first element isa tubulanaupportstructure identified by the `numeral 25 whiclrmay be constitute a conventional drill string ora Tubular. support 25 preferably terminates at its lowerend in an outward and downward llare 30.

` Porta l are `cut. through `the tubular support 25. In

the` particular drill` illustrated, immediately above the outwardly dared portion of the tubular support, an inwardly` extensive shoulder `14` is provided.

'Ibeiaeoond principal element of this drill constitutes what may be identified as a body element 2. This body element is adapted to t within the lower termination of the drillatring so as to seat on the shoulderl 14. Seals 26 may be provided on the body so as to effectively maintain the body within the drill string in huid-tight relation. i The ,body 2 is provided with particularly designed uid which can` be understood by reference to both Figure l and Figure 2 since these channels arenotsymmetrically arranged within the body.` A irstchannel extendsfrorn an upper portion of the body along will `iilcsof thebody to communicate with an internal annular cavity `identified by numeral 5. Cavity 5 is iin communication with the primary nozzles 6 which are spaced about the lower temiinationl of the body so as to `ililectluid how downwardly and outwardly from the body. y y A, seoondiluid channel 28 extends from the lower and central portion of the body upwardly and outwardly to termiulloin the passages 4. 1 Passages `4 are positioned at thesurfaceo! the body which is formed to` have a constrlcted cross-sectional area. Thereby an `annular cavity is provided about the body within the drill string 25. Fluid passingthrough ports 4 can therefore llow through the porta 191 by passage throughcavity 29.

Beneath` the central portion ofthe body ispositioned a central return cylinder or nozzle `10. This cylinder may be positioned `by means of the bars 9 or maybe oonatrucled so as to be integral with thebody assembly. Return cylinder l0 provides a central passagepermitting uptlow of lluid along the axis of the drill, as will be deacribedwhile forming an annular space .detined be- F' 1 illustrates `the operative `featuresof thedrill igurez is a fragmental cross-sectional view of Ille drill illustrated inthe drawings essentially con-;

1 operated can be understood.

llared portion of the tubular support.

With this description andidentiiication of the principal elements of the drill, the manner in which this drill is In operation a plurality of pellets 31 are placed at the bottom of the bore hole. Drilling mud or other luid is then forced downwardly through the drill string from the surface of the earth. the drilling tluid enters the uid channel 3 so as to pass `into thecavity 5 for exhaust through the primary nozzles 6. The passage `of the lluid through these` primary nozzles causes the ietting of a high velocity fluid strm from each of the nozzles.` This lluid stream is directed downwardly through the secondary nozzle arrangement provided by the annular space 32 between the cylinder 10 and the flared portion of the tubular support. The jettcd fluid is therefore directed downwardly and outwardly to contact the walls of the bore hole and to be circulated inwardly and upwardly through the cylinder l0. This uid ilow `is eifective to pick up and entrainthepellets 31 referred to so that these` pellets are foreefullydirected against the outer portion of the bore hole for return inwardly and upwardly through the cylinder 10.

The lower terminationof the central uid passage 28 is provided with a blocking element 11 which is perforated by slots 13 so that fluid can pass through channel a 28 for exhaust to the bore hole annulus` through ports 19. Blocking means 11, however,1 serves to prevent passage of the pellets and to deilectthese pellets into a return circulation path inthe `fluid jetted from nozzle 6. In this manner continuous drilling action cangbe effectively obtained.

In an operative formof the drill describedit is de sirable to position a seal 15 aboutthe lower termination of thetubular support 25 so as to prevent lluid llow between the bore hole and the support 25 at this point. This tluid sealserves to ensure the most eectivecirculation of the drilling tluid as described.`

A spearhead 1 or similar device is preferably `fixed to` the body2 sothat the entire body can be lowered into` place or recovered by use of l a wire line as desired in order to replace the nozzle elements as wear occurs during drilling.

It is apparent that the `drill described is subject to many modifications within the scope of this invention.

What is claimed is: Y

l. A pellet impact drill comprising in combination a tubular support member including `port elements adjacent its lower terminationand having an inwardly projecting shoulder member below said port elements, a removable body element adapted to` lit within the lower portion of said tubular support member in duid-sealed relation there.

with and laterally adjacentsaid port elements and being further adapted to rest upon saidshoulder member, wireline engaging means attached to said body element whereby a wire line may be attached thereto for raisingand loweringsaid body element, a plurality of primary nozzles positioned at the lower termination and spaced about the axis of the body `element directed downwardly and outwardly with respect tothe `body element, a secondary nozzle positioned around and below said primary nozzles and longitudinally aligned therewith, a first channel `in said body element providing uid communication between the interior of said tubularsupportmember and said primary nozzles, a second channel in the central lower portion of the body element to provide liuid communication from below said body element to said port elements, a passageway interconnecting said second channel with the entrance to said secondary nozzle with said passageway being characterized by having pellet-blocking means therein adapted to detlect anyl pellets owing therethrough in to said secondary nozzle and a return nozzle supported within said secondary nozzle and establishing fluid communication from the exterior of said secondary nozzle to said passageway.

2. The drill defined by claim 1 including an outwardly and upwardly extending seal member xed about the external termination of the tubular support and below said port elements.

3. A pellet impact drill comprising in combination a tubular support member including port elements adjacent its lower termination and having an inwardly and upwardly projecting shoulder member below said port elements, a removable body element adapted to fit within the lower portion of said tubular support in duid-sealed relation therewith and laterally adjacent said port elements and being of a character to be supported by said shoulder member, wire-line engaging means attached t0 said body element whereby a wire line may be attached thereto for raising and lowering said body element, a plurality of primary nozzles positioned at the lower termination and spaced about the axis of the body element and directed downwardly and outwardly with respect to said body element, a secondary nozzle constituting an annular opening positioned around and below said primary nozzles in longitudinally aligned relation therewith, a rst channel in said body element providing fluid communication between the interior of said tubular support and said primary nozzles, a second channel in the central lower portion of said body element to provide fluid communication from below said body element to said port elements, a return nozzle supported within said secondary nozzle, a passageway interconnecting said second channel with the entrance to said secondary nozzle and said return nozzle with said passageway being characterized by having pellet-blocking means therein and of a character to deect any pellets owing therethrough into said secondary nozzle.

References Cited in the le of this patent UNITED STATES PATENTS 1,557,131 Armstrong Oct. 13, 1925 2,072,627 Zublin Mar. 2, 1937 2,233,260 Hawthorne Feb. 25, 1941 2,525,391 Bates Oct. 10, 1950 2,708,567 Hildebrandt May 17, 1955 2,724,575 Deily Nov. 22, 1955 2,743,086 Roth Apr. 24, 1956 

